JP4775521B2 - Mold for casting - Google Patents

Description

  The present invention relates to a casting mold used in die casting or the like.

2. Description of the Related Art Conventionally, a die casting method such as die casting has been used to manufacture engine parts constituting an automobile such as a cylinder head and a manifold from a non-ferrous metal such as aluminum. In the mold casting method, when the flow of molten metal (hot water flow) in the mold deteriorates during casting, defects such as minute shrinkage and hot water wrinkles are likely to occur in the cast product. Various ideas have been made for this purpose. As a method for improving the molten metal flowability, it is necessary to form an uneven portion on the mold surface (cavity surface) to rectify the flow of the molten metal so that the molten metal flows over the entire cavity surface. It is.
As a method for improving the flowability of the molten metal by forming an uneven portion on the cavity surface, for example, Patent Document 1 discloses that a rectangular mold concave portion and a mold cavity so as to spread adjacent to the cavity surface of a mold. A mold convex part is formed continuously, and a portion having a large molten metal flow resistance and a small part are alternately configured, and the direction of one side of the rectangular mold concave part and the mold convex part is set with respect to the injection direction of the molten metal. A die casting mold is disclosed in which the injected molten metal is uniformly filled in each part of the cavity by tilting the mold.
JP 7-246450 A

Here, in the technique as described above, the concavo-convex portion is formed by embossing or electric discharge machining that forms the concavo-convex portion by corroding the cavity surface with a nitric acid-based corrosion liquid or the like. However, these machining methods have a problem that the range in which the cavity surface can be machined is limited, and a mold having a complicated cavity shape cannot obtain sufficient molten metal flow. In addition, the texture processing has a problem in that it is difficult to form a concavo-convex portion whose size, depth, shape, and the like are highly controlled, so that sufficient hot water flow cannot be obtained.
In addition, since the shape of the concavo-convex portion to be formed is square, galling or the like is likely to occur when the cast product is released from the mold, and the ease of release from the mold (releasability) is reduced. There was a problem. When the concavo-convex part has directionality in one direction, the release agent for improving the releasability when applied to the cavity surface becomes difficult to stay uniformly on the cavity surface, so the releasability is reduced. There was a problem to do.

  Accordingly, an object of the present invention is to realize a casting mold that has good hot metal flowability, excellent mold releasability, is difficult to seize, and has excellent durability.

The present invention is a casting mold for achieving the above object, and in the invention according to claim 1, a plurality of first dimples have no directionality on at least a part of the cavity surface and the runner. A casting mold having dispersedly formed dimple regions, wherein the first dimple has a hemispherical depth, and two or more dimples with respect to the total number of the first dimples The technical means that the communication rate defined by the ratio of the number of the first dimples connected to each other is 80% or more is used.
Here, the “dimple region” is a region defined surrounding the outermost periphery of the first dimple.

According to the first aspect of the present invention, the casting mold includes a dimple region in which the first dimple is formed in the cavity surface and at least a part of the runner and is uniformly dispersed without directivity. By forming the dimples so as to have a communication rate of 80% or more, a number of short flow paths that are random and have no directivity are formed in the dimple region by combining several first dimples. . Among the molten metal flowing through the first dimple, the molten metal that has entered the flow path described above changes in the direction of flow at random, so that the molten metal can be spread and spread uniformly in the cavity. Can be improved.
By improving the hot water flowability, casting defects such as pinholes, hot water boundaries, and hot water wrinkles due to gas entrainment can be reduced.
Further, since the first dimple is formed into a hemispherical dimple, the release agent applied to the cavity surface during casting can be easily retained. In addition, unlike dimples formed by embossing, etc., it is formed into a hemispherical shape without corners, so that no galling or the like occurs at the time of mold release, and the cast product can be easily released. You can avoid scratching.

  In the invention according to claim 2, the first dimple is formed so that the diameter of the opening is 60 to 500 μm and the depth is 4 to 30 μm, and the area ratio of the first dimple to the dimple region is The technical means is that it is 50-90%.

  Since the first dimple is preferably formed as a shallow hemispherical dimple whose opening has a diameter of 10 times or more with respect to the depth, as in the invention according to claim 2, the first dimple is Preferably, the opening has a diameter of 60 to 500 μm and a depth of 4 to 30 μm, and the area ratio with respect to the dimple region is 50 to 90%. Furthermore, as described in claim 3, the area ratio is more preferably 71 to 86%. In order to increase the communication rate to 80% or more as described in claim 1, the area ratio of the invention is preferably set to 50% or more as in this item (claim 2), and the area ratio is 90%. If it exceeds 1, most of the first dimples overlap when the first dimple is formed, and the shape cannot be made hemispherical. Thereby, since it becomes difficult to hold | maintain a mold release agent, mold release property worsens. In addition, since the end portion of the first dimple is in an angular state, problems such as galling occur at the time of mold release of the cast product. Therefore, the area ratio is preferably 90% or less.

  According to a fourth aspect of the present invention, there is provided a technical means in which a second dimple having a size smaller than that of the first dimple is formed in the dimple region so as to be mixed with the first dimple. Use.

  According to the fourth aspect of the present invention, since the second dimple having a size smaller than that of the first dimple is formed in the dimple region in combination with the first dimple, the first dimple in the dimple region is formed. A portion where no slab is formed can be made to have a non-directional surface property by eliminating a machining mark or the like due to machining of the cavity surface. As a result, the first dimple and the second dimple can be uniformly dispersed on the cavity surface without directionality. Therefore, the first dimple and the second dimple are (1) a gold in contact with the molten metal. Due to the increase in the mold surface area, the temperature of the molten metal is easily transmitted to the mold, and the mold is not easily cooled. (2) Among the irregularities, the air layer formed in the large concave portion (first dimple) is the temperature of the molten metal. There is also a warming action of the molten metal, such as not lowering the hot water flow, and the hot water flowability can be improved. In addition, since the release agent can be easily held in the portion of the dimple region where the first dimple is not formed, the releasability can be improved.

  According to a fifth aspect of the present invention, there is used a technical means that the second dimple is hemispherical and formed so that the opening has a diameter of 10 to 60 μm and a depth of 1 to 7 μm. .

  The second dimple is formed to eliminate surface traces with no directivity by eliminating machining marks or the like due to machining of the cavity surface, etc., and to improve the hot water flow, and the surface roughness is more than necessary. It is preferable not to make it large. For example, the surface roughness Rz (ten-point average roughness) may be about several μm. By forming the second dimple as in the fifth aspect of the invention, it is possible to eliminate a processing mark due to machining of the cavity surface and the like to obtain a surface property having no directivity, and to improve the flowability of molten metal. It is possible to obtain a shape suitable as a surface shape having minute irregularities.

  The invention according to claim 6 uses a technical means that the cavity surface is nitrided.

  According to the invention described in claim 6, since the nitriding treatment is performed on the cavity surface, the durability of the mold can be improved and the life of the mold can be extended.

  In the invention according to claim 7, the technical means that the dimple region is provided in the runner is used.

  According to the seventh aspect of the present invention, since the dimple region is provided in the runner, the resistance of the molten metal to pass through the runner can be reduced when the molten metal is poured into the cavity. The flow of the molten metal injected into the inside is not hindered. Thereby, the molten metal flow property in the cavity can also be improved.

  In the invention according to claim 8, the technical means that the dimple region is provided on the bottom surface of the cavity surface is used.

  According to the eighth aspect of the present invention, the dimple region is provided on the bottom surface portion of the cavity surface where the molten metal injected into the cavity is always in contact, so that the molten metal flows more effectively. Can be improved.

  In a ninth aspect of the invention, a technical means is used in which the dimple region is provided on a standing surface portion extending in the mold opening / closing direction in the cavity surface.

  The standing surface portion extending in the mold opening / closing direction of the cavity surface is a portion where the release agent easily flows down and is detached, and galling or the like is likely to occur when the cast product is released. As in the ninth aspect of the invention, by providing the dimple region on the standing surface portion of the cavity surface, the occurrence of the above problem can be suppressed.

  In a tenth aspect of the present invention, technical means is used in which the dimple region is provided on a convex portion of the cavity surface.

  The convex portion of the cavity surface is a portion where the release agent is easily detached and seizure or galling is likely to occur when the cast product is released. As described in the tenth aspect, by providing the dimple region on the convex portion of the cavity surface, the occurrence of the above problem can be suppressed.

In the invention described in claim 12, the technical means that the dimple region is provided in the concave portion of the cavity surface is used.

  The invention according to claim 13 uses technical means that the concave portion of the cavity surface is a corner portion. The concave portion of the cavity surface is a location where stress is concentrated and is a location where heat cracks are likely to occur conventionally. In particular, the corner is remarkable. According to the twelfth aspect of the present invention, since the dimple region is provided in the concave portion of the cavity surface, the dimple is formed in the corner portion, particularly in the corner portion, and the stress is distributed, so that heat cracks are generated. Can be prevented. The shape of the corner when the dimple region is provided in the concave portion is exemplified in FIG. 5C, for example, but is not limited to this shape.

  In the invention described in claim 14, the technical means that the first dimple is formed by blasting is used.

  According to the fourteenth aspect of the present invention, the first dimple can be formed on a cavity surface of a mold having a complicated cavity shape by forming by blasting, and also used for blasting. By appropriately selecting the material, the injection conditions, etc., the first dimples having the desired dimensions, area ratio, and communication ratio can be easily formed.

The invention according to claim 11 uses technical means that the convex portion of the cavity surface is a corner.
As described above, by using the blasting method for providing the dimple region on the convex portion of the cavity surface, the processed surface is removed or plastically deformed, so that the corner portion of the convex portion is chamfered. In particular, the corners of the convex part of the cavity surface in the mold are places where the release agent is difficult to adhere, and seizure or galling is likely to occur when the cast product is released, and it is also the place where heat cracks are based. Since the corners are chamfered by blasting, the release agent is easily attached, the seizure and galling are less likely to occur, and the stress is dispersed to prevent the occurrence of heat cracks. The shape of the corner is exemplified in FIG. 5B, for example, but is not limited to this shape.

  The invention according to claim 15 uses a technical means that when the second dimple is formed in the dimple region, the second dimple is formed by blasting.

  According to the fifteenth aspect of the present invention, the second dimple can be formed on the cavity surface of a mold having a complicated cavity shape by being formed by blasting, and also used for blasting. The second dimple having a desired dimension can be easily formed by appropriately selecting a material, injection conditions, and the like.

As is clear from the above description, in the conventional casting mold, when about 50,000 products are cast, seizure and heat cracks occur and repair is required, and sometimes renitriding is also required. there is, blasting method casting mold which has been subjected to the present invention, dimples are formed in corners of the corners and concave portion of the convex portion fraction of the cavity surface is chamfered stress distribution shape together comprising, conventionally, also it can be easily attached to the corners of the standing surface portion and the convex portion fraction of the cavity surface was then hardly adhered release material, also the holding force of the release material also can be thereby increased, 100,000 Providing a casting mold with excellent durability that can maintain good hot-water flow properties even when casted products, does not cause seizure or heat cracks, and does not require renitriding. it can.

It is explanatory drawing which shows the structure of the metal mold | die for casting which concerns on this embodiment. FIG. 1A is a cross-sectional explanatory view of one of the casting molds in an open state, and FIG. 1B shows a part of the dimple region provided on the bottom surface of the cavity surface in FIG. It is the plane expansion schematic diagram seen from the X direction, and FIG.1 (C) is AA arrow sectional drawing of FIG.1 (B). It is explanatory drawing which shows typically the effect of the hot water flow improvement by a dimple area | region. It is sectional explanatory drawing which shows the example of a change of a dimple area | region. It is explanatory drawing which illustrates the position which provides a dimple area | region. 4A is an explanatory plan view as viewed from the opening of the casting mold, and FIG. 4B is a cross-sectional view taken along the line BB in FIG. 4A. It is explanatory drawing which illustrates the state from which the corner | angular part of the convex part of the casting mold was removed and the recessed part was corrected. FIG. 5 (A) is an overall view of a casting mold provided with a dimple region, FIG. 5 (B) is an enlarged view of a portion A in FIG. 5 (A), and FIG. FIG. In the casting mold of Example 1, it is explanatory drawing which shows the quality determination result of the cast product by the area ratio of 1st dimple, a communication rate, the plane image of a dimple area | region, and each casting mold.

  The casting mold of the present invention will be described with reference to the drawings, taking as an example a mold having a dimple region in which a first dimple is formed on the bottom surface of the cavity surface.

  The casting mold of this embodiment is a casting mold used for die casting of aluminum alloy or the like, for example. In FIG. 1, the mold 10 is in an open state, and only one side is shown. As shown in FIG. 1, the mold 10 includes a dimple region D composed of a first dimple 12 and a second dimple 13 on the bottom surface portion 11 a of the cavity 11. Here, the dimple region D is a region surrounding the outermost periphery of the first dimple 12, and in the present embodiment, the dimple region D is formed on substantially the entire bottom surface portion 11 a.

  The first dimples 12 are formed as hemispherical dimples having a shallow depth, and are uniformly dispersed in the dimple region D without directivity. In the dimple region D, a single dimple 12a, which is one hemispherical first dimple 12, and a combined dimple 12b in which a plurality of first dimples 12 are combined to form a short flow path are formed. Has been.

  Here, when the number of the single dimples 12a is A and the number of the first dimples 12 constituting the coupled dimple 12b is B, B / (A + B), that is, 2 to the total number of the first dimples 12. The “communication rate” is defined by the ratio of the number of the first dimples 12 constituting the coupled dimple 12b in which the above dimples are coupled.

  By forming the first dimples 12 in the dimple region D of the mold 10 so that the defined communication rate is 80% or more and uniformly dispersed without directivity, the flow path is random and has no directivity. A large number of coupled dimples 12b are formed. As schematically shown in FIG. 2, most of the molten metal injected into the cavity from the pouring port 14a through the runner 14 enters the coupling dimple 12b. As shown by the arrows in the figure, the flow of the molten metal that has entered the coupling dimple 12b changes randomly, so that the molten metal can be spread uniformly in the cavity, so that the molten metal flow can be improved. Casting defects such as pinholes, hot water boundaries, and hot water wrinkles due to gas entrainment can be reduced.

  Since the first dimple 12 is formed into a hemispherical dimple, the mold release agent applied to the cavity surface 11 during casting can be easily retained. In addition, unlike dimples formed by embossing, etc., it is formed into a hemispherical shape without corners, so that no galling or the like occurs at the time of mold release, and the cast product can be easily released. You can avoid scratching.

In order to achieve the above-described effects more effectively, the first dimple 12 is preferably formed as a shallow hemispherical dimple whose opening diameter is 10 times or more of the depth. Is 60 to 500 μm, the depth is 4 to 30 μm, and the area ratio to the dimple region D is preferably 50 to 90%.
In order to increase the communication rate to 80% or more, the area rate needs to be 50% or more. However, when the area rate is 90% or more, most of the first dimples 12 are overlapped. Since the shape of the first dimple 12 cannot be made hemispherical, the release agent is difficult to hold and the releasability is deteriorated. In addition, since the end portion of the first dimple 12 is in an angular state, problems such as galling occur at the time of mold release of the cast product occur. Therefore, the area ratio is preferably 90% or less.

  The second dimple 13 is formed with a size smaller than that of the first dimple 12 and is formed in the dimple region D in a mixed manner. In the present embodiment, as shown in FIG. 1C, the second dimple 13 is formed in a region of the dimple region D where the first dimple 12 is not formed.

  Since the second dimple 13 is formed in this way, the portion of the dimple region D where the first dimple 12 is not formed also has no directionality due to the removal of a processing mark or the like due to machining of the cavity surface 11 or the like. Surface texture can be obtained. Thereby, the first dimple 12 and the second dimple 13 can be uniformly dispersed on the cavity surface 11 without directionality, and the unevenness formed by the first dimple 12 and the second dimple 13 Further, (1) the surface area of the mold that comes into contact with the molten metal is increased, whereby the temperature of the molten metal is easily transmitted to the mold, and the mold is difficult to be cooled. (2) Among the concaves and convexes, the large concave portion (first dimple 12 Since the air layer formed in (2) has a heat retaining action of the molten metal such as not lowering the temperature of the molten metal, the flowability of the molten metal can be improved. In addition, since the release agent can be easily held in the portion of the dimple region D where the first dimple 12 is not formed, the releasability can be improved.

  In order to achieve the above-described effect more effectively, it is preferable that the second dimple 13 does not have an unnecessarily large surface roughness. For example, the surface roughness Rz (ten-point average roughness) may be about several μm. By forming the second dimple 13 so as to have a hemispherical shape with an opening having a diameter of 1-60 μm and a depth of 0.1-7 μm, machining marks and the like due to machining of the cavity surface 11 are eliminated. It can be made into a shape suitable as a surface shape having minute irregularities for improving the hot water flowability, while having a surface property having no directionality.

  In the above-described embodiment, the second dimple 13 is formed in a region where the first dimple 12 is not formed in the dimple region D. As another embodiment, as shown in FIG. It can also be formed inside the first dimple 12. Since the molten metal flow state changes depending on the shape of the product to be cast, that is, the shape of the cavity surface 11, a surface property that matches the difference may be selected.

  When the cavity surface 11 does not have a large processing mark or the like due to machining or the like that impedes hot water flow, the second dimple 13 may not be formed in the dimple region D. Further, the second dimple 13 can be formed in a region other than the dimple region D in order to remove a processing mark or the like due to machining or the like of the cavity surface 11.

  The cavity surface 11 of the mold 10 may be surface-modified by heat treatment after the dimple region D is formed, or a film may be formed by nitriding treatment or the like. Thereby, durability of the metal mold | die 10 can be improved and the lifetime of the metal mold | die for casting can be extended. Further, before forming the dimple region D, a film may be formed by heat treatment to modify the surface or by nitriding treatment, but in this case, the first dimple 12 and the second dimple 13 are formed. At this time, it is preferable to use a spherical injection material and appropriately set the formation conditions so that the coating film is not damaged.

  An example of the process for forming the first dimple 12 and the second dimple 13 described above will be described below.

  First, the second dimple 13 is formed over the entire region where the dimple region D is to be formed. The second dimple 13 is formed by blasting the cavity surface 11 using an injection material made of a material having a hardness equal to or higher than the hardness of the constituent material of the mold 10. The second dimple 13 preferably does not have an unnecessarily large surface roughness. For example, the cavity surface 11 having a surface roughness Rz (ten-point average roughness) of about several μm may be formed.

  In order to form such a cavity surface 11, the following characteristics are required for the injection material. First, it is necessary to have a hardness equal to or higher than the hardness of the constituent material of the mold 10. Examples of the material for the casting mold include hot tool alloy tool steel SKD61 (JIS G 4404) used for die casting of an aluminum alloy or the like. Some of these materials have a Vickers hardness Hv as high as about 500, and it is preferable to use a high-hardness injection material having a Vickers hardness Hv of 500 or more, preferably 700 or more.

  In order to form the cavity surface 11 having a surface roughness Rz of about several μm, the particle size of the propellant is preferably about 10 μm to 100 μm.

  The shape of the injection material can be indefinite, spherical, or other shapes, but if an indeterminate type of injection material is used, its grinding action will work, and the cavity surface 11 will be ground to obtain the dimensional accuracy of the mold 10. Therefore, it is preferable to use a spherical injection material mainly having a plastic deformation action for forming the dimples. Moreover, when a spherical injection material is used, the peening effect by provision of a residual stress can also be show | played and the lifetime of the metal mold | die 10 can also be improved.

Examples of the injection material that satisfies the above-described characteristics include, for example, irons described in Japanese Patent Application Laid-Open No. 2002-80949 (Japanese Patent No. 4317930) and Japanese Patent Application Laid-Open No. 2005-76083, which were previously filed by the applicant of the present invention. System amorphous spherical particles and the like can be suitably used.

Subsequently, the first dimple 12 having a hemispherical shape larger than the second dimple 13 is mixedly formed on the second dimple 13. The formation of the first dimple 12 is made of a material having a hardness equal to or higher than the hardness of the constituent material of the mold 10, and a spherical injection material having a particle diameter larger than that of the injection material used for forming the second dimple 13 is used. Then, the region where the dimple region D is formed is performed by blasting.
Here, the first dimple 12 is formed so that the communication rate is 80% or more.

  Such a first dimple 12 is preferably formed as a shallow hemispherical dimple whose opening diameter is 10 times or more of the depth. Therefore, the particle diameter of the injection material is about 100 μm to 1000 μm. Preferably there is. Further, the area ratio of the first dimple 12 to the dimple region D is preferably 50 to 90%, and more preferably about 70%.

  In order to perform die casting using the mold 10 in which the dimple region D is formed on the cavity surface 11 as described above, first, a release agent such as boron nitride is applied to the cavity surface 11 of the mold 10. . Subsequently, a molten metal such as an aluminum alloy is poured into the cavity. Then, the molded product formed by solidification of the molten metal is extruded from the mold with an extrusion pin or the like and released.

  Here, since the dimple region D is formed as a surface in which the second dimple 13 and the first dimple 12 are mixed, the hot water flow is good, and the holding power of the release agent of the first dimple 12 is high. Since it is good and excellent in releasability, it is possible to produce a good cast product that does not cause defects such as pinholes and water wrinkles. Further, when the first dimple 12 and the second dimple 13 are formed by blasting, they can be easily formed even on the cavity surface of a mold having a complicated cavity shape.

When the dimple region D is formed by blasting, it can be easily formed at any position where the hot-water flow property and the release property are to be improved. For example, as shown in FIG. 4, in addition to the bottom surface portion 11 a, a runway 14 that is a path for injecting molten metal into the cavity, a standing surface portion 11 b that extends in the opening and closing direction of the mold 10, a convex portion 11 c of the cavity surface 11, etc. Can be formed.
When the dimple region D is formed in the runner 14, the resistance of the melt passing through the runner when pouring the melt into the cavity can be reduced, so that the flow of molten metal injected into the cavity is not hindered. Thereby, the molten metal flow property in the cavity can also be improved. The standing surface portion 11b is a portion where the release agent tends to flow downward and detach, and galling or the like is likely to occur when releasing the cast product. By providing the dimple region D on the standing surface portion 11b, the occurrence of the above problem can be suppressed.
The convex portion 11c of the cavity surface 11 is a portion where the release agent is easily detached, galling is likely to occur when the cast product is released, and heat cracks are likely to occur. By providing the dimple region D on the convex portion 11c, the occurrence of galling or the like can be suppressed. Further, as shown in FIG. 5, at this time, the corner 11d of the convex portion is chamfered and the acute angle surface is removed, thereby preventing the welding of the cast product to the corner 11d and the lacking phenomenon of the cast product, and Generation of heat cracks can be prevented.
Further, the concave portion of the cavity surface 11, particularly the corner portion, is a place where heat cracks are likely to occur. By providing the dimple region D in the concave portion, the dimples are also formed in the corner portion 11e corresponding to the concave portion and the stress is dispersed, thereby preventing the occurrence of heat cracks.
By forming the dimple region D only at a location where it is necessary to improve the molten metal flow and mold release properties, the surface roughness of the cast product can be reduced, and the appearance characteristics of the product can be improved. For example, when forming in the bottom face part 11a, if it forms in the pouring hole 14a vicinity, a molten metal can be spread more efficiently and a molten metal flow property can be improved.
In addition, the effect of the unevenness formed by the first dimple 12 and the second dimple 13 in the dimple region D is as follows. (1) The surface area of the mold in contact with the molten metal is increased, so that the temperature of the molten metal becomes the mold. (2) The air layer formed in the large concave part among the concaves and convexes has a heat retaining effect by preventing the temperature of the molten metal from being lowered. Can be made.

Example 1
In this example, a thin plate material was cast with a casting mold in which the dimple region D was formed, and the influence of the communication rate of the first dimple 12 on the quality of the cast product was confirmed. In addition, this invention is not limited to the following embodiment.

The mold used in this example is made of alloy tool steel SKD61 (hardness is Hv 470 to 500). First, the second dimple 13 was formed on the cavity surface 11. The second dimple 13 uses a gravity-type blasting apparatus “My Blast” ^TM (MY-30A, manufactured by Shinto Kogyo Co., Ltd.), and has a hardness of Hv900 and an average particle diameter of 50 μm. ^TM (manufactured by Shinto Kogyo Co., Ltd. AM-50) was formed by spraying for 10 seconds under the conditions of an injection pressure of 0.3 MPa, an injection distance of 100 mm, and a nozzle angle of 90 °.

  Subsequently, the first dimple 12 was formed by changing the area ratio, and the dimple region D was formed. In this embodiment, the entire cavity surface 11 is the dimple region D. The first dimple 12 uses a direct pressure blasting device (MY-30AP manufactured by Shinto Kogyo Co., Ltd.), and has a spherical steel shot (SB- manufactured by Shinto Kogyo Co., Ltd.) with a hardness of Hv700 and a particle size of 600 μm. 6PH) was injected under the conditions of an injection pressure of 0.5 MPa, an injection distance of 100 mm, and a nozzle angle of 90 °.

  As a result, the dimple region D can be formed in such a manner that the second dimple 13 and the first hemispherical dimple 12 having a shallow depth are uniformly dispersed and mixed. The depth of the first dimple 12 was approximately 13 μm, and the opening was a shallow hemispherical surface with a diameter of approximately 240 μm.

  The area ratio with respect to the dimple region can be controlled by the injection time when forming the first dimple 12, and for comparison with the five-level mold 10 having an area ratio of 28 to 97%, Thus, a mold 10 in which one dimple 12 is not formed (area ratio 0%) was produced.

  Here, the area ratio was calculated using a binarized image obtained by photographing a dimple region with a CCD camera and binarizing the obtained image. Further, the communication rate was calculated from the ratio obtained by counting the total number of dimples and the original number of dimples connecting adjacent dimples from the image obtained by the CCD camera.

Casting experiments were performed using six types of molds 10, and the influence of the communication rate of the first dimples 12 on the quality of the cast product was confirmed. The molten metal used was an aluminum alloy (ADC12: density 2.72 g / cm ³ ), and poured into the cavity at a molten metal temperature of 700 ° C. and a mold temperature of 300 ° C. The quality of the cast product was judged after release.

  In the determination of the quality of the mold, when a certain amount of cast product is manufactured, the number A of defective products of the cast product manufactured using the mold of the present invention is calculated using the mold in which the dimple region D is not formed. The ratio was determined by the ratio (A / B) divided by the number B of defective castings produced. It can be determined that the smaller the value is, the higher the improvement effect is, and the determination criteria are set as follows.

○: A / B = less than 50% Δ: A / B = 50-90%
×: A / B = over 90%

  As shown in FIG. 6, the larger the area ratio, the greater the number of coupled dimples 12b in which a plurality of dimples are coupled, resulting in an increase in communication rate. When the area ratio was 50% or more, the communication rate was 80% or more.

The result of the quality determination of the cast product is x or Δ when the area ratio is less than 50% (0%, 28%) and when the area ratio exceeds 90% (97%), and the dimple region D There was no significant improvement effect due to the formation of. Casting defects when the area ratio is less than 50% (0%, 28%) are blistering, skin peeling, hot water wrinkles, hot water boundaries, seizures, etc., which are caused by insufficient hot water flow. . The casting failure when the area ratio exceeded 90% was caused by poor release properties such as galling.
On the other hand, when the mold 10 having an area ratio of 50%, 71%, 86%, that is, a communication rate of 80% or more was used, the quality judgment result of the cast product was “good”.
As a result, in the dimple region D, the first dimple 12 is formed so that the communication rate is 80% or more, that is, the area ratio is 50 to 90%. In comparison, it was confirmed that the hot water flowability and mold releasability were improved.

(Example 2)
The alloy tool steel SKD61 was blasted, and the relationship between the depth of the first dimple 12 and the second dimple 13 and the diameter of the opening was investigated. The first dimple 12 injects an injection material (steel shot) made of three types of steel balls having an average particle diameter of 100, 600, and 1000 μm under the conditions of an injection pressure of 0.5 MPa, an injection distance of 100 mm, and a nozzle angle of 90 °. Was formed. The second dimple 13 was formed by injecting an injection material composed of spherical amorphous particles having an average particle diameter of 50 and 100 μm and spherical alumina particles having an average particle diameter of 20 μm under the same conditions. Table 1 shows the relationship between the depth of the dimple measured from the cross-sectional photograph and the diameter of the opening.

  From Table 1, the first dimple 12 having an opening diameter of 75 to 380 μm and a depth of 5 to 21 μm is obtained by blasting using an injection material having an average particle diameter of 100 to 1000 μm. It was confirmed that the second dimple 13 having an opening diameter of 12 to 61 μm and a depth of 1 to 7 μm can be formed by blasting using a 100 μm injection material.

[Effect of the embodiment]
According to the mold 10 of the present invention, the dimple region D in which the first dimples 12 are uniformly dispersed without directionality is provided on at least a part of the cavity surface 11 and the runner 14 of the mold 10. In addition, by forming the first dimple 12 in the dimple region D so that the communication rate thereof is 80% or more, the coupled dimple 12b of the first dimple 12 becomes a short flow path having random and no directivity. Are uniformly dispersed in a large number. Of the molten metal flowing via the coupling dimple 12b of the first dimple 12, the flowing direction of the molten metal that has entered the above-described flow path changes randomly, so that the molten metal is uniformly spread in the cavity. And the unevenness formed in the dimple region D further increases (1) the surface area of the mold that comes into contact with the molten metal, so that the temperature of the molten metal is easily transmitted to the mold, and the mold is not easily cooled. (2) Since the air layer formed in the large concave portion among the concaves and convexes also has a heat retaining action of the molten metal such as not lowering the temperature of the molten metal, it is possible to improve the flowability of the molten metal.
By improving the hot water flowability, casting defects such as pinholes, hot water boundaries, and hot water wrinkles due to gas entrainment can be reduced.
Furthermore, since the first dimple 12 is formed into a hemispherical dimple, the release agent applied to the cavity surface 11 during casting can be easily retained. In addition, unlike dimples formed by embossing, etc., by forming a semispherical shape without corners, no galling or the like occurs when the cast product is released, making it easier to release the cast product. You can avoid scratching.

Since the second dimple 13 having a size smaller than that of the first dimple 12 is formed in the dimple region D so as to be mixed with the first dimple 12, the first dimple 12 in the dimple region D is formed. The unexposed portion can be made to have a non-directional surface property by eliminating a machining mark or the like due to machining or the like of the cavity surface 11. As a result, the first dimple 12 and the second dimple 13 can be uniformly dispersed on the cavity surface 11 without directivity, and the unevenness formed in the dimple region D further causes (1) contact with the molten metal. As the surface area of the mold increases, the temperature of the molten metal is easily transmitted to the mold, and the mold is not easily cooled. (2) The air layer formed in the large concave portion among the concaves and convexes does not lower the temperature of the molten metal. Since there is also a heat retaining action of the molten metal such as, and the like, it is possible to improve the hot water flow.
In addition, since the release agent can be easily held in the portion of the dimple region D where the first dimple 12 is not formed, the releasability can be improved.

  When the cavity surface 11 is subjected to nitriding treatment, the durability of the mold 10 can be improved and the mold life can be extended.

  The first dimple 12 and the second dimple 13 are formed by blasting, so that the dimple region D is freed from the runner 14, the bottom surface portion 11 a, the standing surface portion 11 b, and the mold release agent that are required to have molten metal flow. Since it can form in the convex part of the cavity surface 11 which is easy to release and a galling etc. are easy to generate | occur | produce at the time of mold release of a cast product, molten metal flow property and mold release property can be improved further. In addition, it can be formed on the cavity surface of a mold having a complicated cavity shape, and by appropriately selecting the injection material and injection conditions used for blasting, dimples with a desired size and area ratio can be easily obtained. Can be formed.

[Other Embodiments]
In the embodiment described above, the mold mainly used for die casting has been described. However, the present invention is not limited to this, and for the mold used for various casting methods such as low pressure casting and suction differential pressure casting. Can be applied.

This application is based on Japanese Patent Application No. 2009-185341 filed on August 8, 2009 and Japanese Patent Application No. 2009-269666 filed on November 27, 2009 in Japan. A part of it is formed.
The present invention will also be more fully understood from the detailed description herein. However, the detailed description and specific examples are preferred embodiments of the present invention and are described for illustrative purposes only. This is because various changes and modifications will be apparent to those skilled in the art from this detailed description.
The applicant does not intend to contribute any of the described embodiments to the public, and the disclosed modifications and alternatives that may not be included in the scope of the claims are equivalent. It is part of the invention under discussion.
In this specification or in the claims, the use of nouns and similar directives should be interpreted to include both the singular and the plural unless specifically stated otherwise or clearly denied by context. The use of any examples or exemplary terms provided herein (eg, “etc.”) is merely intended to facilitate the description of the invention and is not specifically recited in the claims. As long as it does not limit the scope of the present invention.

10 mold 11 cavity surface 11a bottom portion 11b standing face portion 11c protruding portions partial 11d corner 11e corners 12 first dimple 12a alone dimple 12b coupled dimple 13 second dimple 14 runner D dimple region

Claims (15)

A casting mold provided with a dimple region in which a plurality of first dimples are dispersed in a non-directional manner on at least a part of a cavity surface and a runner,
The first dimple is formed in a hemispherical shape,
A casting mold characterized in that a communication rate defined by a ratio of the number of the first dimples in which two or more dimples are combined to the total number of the first dimples is 80% or more.   The first dimple is formed so that an opening has a diameter of 60 to 500 μm and a depth of 4 to 30 μm, and an area ratio of the first dimple to the dimple region is 50 to 90%. The casting mold according to claim 1, wherein the mold is a casting mold.   The first dimple is formed so that an opening has a diameter of 60 to 500 μm and a depth of 4 to 30 μm, and an area ratio of the first dimple to the dimple region is 71 to 86%. The casting mold according to claim 1, wherein the mold is a casting mold.   The second dimple having a size smaller than that of the first dimple is formed in the dimple region in a mixed manner with the first dimple. Mold for casting.   5. The casting mold according to claim 4, wherein the second dimple has a hemispherical shape and has an opening with a diameter of 10 to 60 μm and a depth of 1 to 7 μm.   The casting mold according to any one of claims 1 to 5, wherein the cavity surface is nitrided.   The casting mold according to any one of claims 1 to 6, wherein the dimple region is provided in the runner.   The casting mold according to any one of claims 1 to 7, wherein the dimple region is provided on a bottom surface portion of the cavity surface.   The casting mold according to any one of claims 1 to 8, wherein the dimple region is provided on a standing surface portion extending in a mold opening / closing direction in the cavity surface.   The casting mold according to any one of claims 1 to 9, wherein the dimple region is provided on a convex portion of the cavity surface.   The casting mold according to claim 10, wherein the convex portion of the cavity surface is a corner portion.   The casting mold according to claim 1, wherein the dimple region is provided in a concave portion of the cavity surface. The casting mold according to claim 12, wherein the casting mold is a corner portion which is a concave portion of the cavity surface and is a portion where heat cracks are likely to occur .   The casting die according to any one of claims 1 to 13, wherein the first dimple is formed by blasting.   15. When the second dimple is formed in the dimple region, the second dimple is formed by blasting. Mold for casting.

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